1. Field of the Invention
The present invention relates to powerfold mechanism for external rear vision mirrors of motor vehicles.
2. Description of the Related Art
Motor vehicles typically have two external rear vision mirror assemblies. The mirror assemblies typically have a mirror head that is designed to rotate about a substantially vertical pivot axis in both forward and rearward directions. The mirror head is typically held in its driving or deployed position by a detent which allows manual movement of the mirror head to a parked position and manual movement to a forward position. There are a number of reasons for this. One reason is safety. By having a mirror that can “break away” to move from a deployed position to a parked or forward position, injury to people can be avoided or at least minimised. Furthermore, damage to the mirror head can be avoided or at least minimised by allowing it to move when it hits obstructions. It is also useful to have a mirror head that can be parked, that is rotated to a position substantially parallel to the side of the vehicle, so as to narrow the effective width of the vehicle. This is particularly useful when the vehicle is parked. It is also useful for loading vehicles onto trucks for transport to be able to park the mirror heads.
Modern external rear vision mirrors, in addition to having a detent mechanism to hold the mirror head in a deployed position while at the same time enabling forward folding and rearward folding of the mirror head, also have electric drive systems to allow the operator to drive the head at least to its parked position. Some external rear view mirror assemblies have more sophisticated electric systems that allow the operator to redeploy the mirror head to a deployed position after it has been manually pushed forward or rearward. These mirror systems are typically referred to as powerfold mirrors.
Powerfold mirrors typically employ powerfold mechanisms that include springs to hold detents in place such that a predetermined force is required to manually break the mirror head out of the detent. A problem with many powerfold mechanisms is that, once they have been manually folded forward thereby breaking the mirror head out its detent, they cannot be reset at the deployed position electrically. Problems with other mechanisms include core vibration performance caused by lack of stability through the powerfold components.
U.S. Pat. No. 6,022,113 (Stolpe et al.) discloses a rear view mirror for a vehicle that can be pivoted both manually and electrically. A clutch between the mirror head and the base, in the form of latching cams on a base and recesses within a gear wheel, is described that allows the mirror head to be manually pivoted. Two drive stops are formed as an integral part of the housing. The drive stops are sloping faces on the housing that contact raised features on the base. The drive stops cannot be used to reset the clutch at the drive position after a manual fold. Instead the mirror head must be electrically driven against an end stop or fold path limiter so as to create the required reaction torque and rotation to reset the clutch.
It is an object of the present invention to provide an improved powerfold mechanism that overcomes at least some of the problems outlined above or at least offers a useful choice.